Biomedical subjects

Matthew D Robson

Publications and source records attributed to Matthew D Robson.

At least 19 recordsLinked to original sources

PubMed2007

Irreversible myocardial injury: assessment with cardiovascular delayed-enhancement MR imaging and comparison of 1.5 and 3.0 T--initial experience.

PURPOSE: To prospectively compare visualization and quantification of irreversible myocardial injury in patients with chronic myocardial infarction at 1.5- and 3.0-T magnetic resonance (MR) imaging. MATERIALS AND METHODS: The institutional research ethics committee approved the study. Participants gave written informed consent. Sixteen male patients (mean age, 66 years +/- 13 [standard deviation]) with myocardial infarction were imaged with the same sequence by the same operator at 1.5 and 3.0 T. After cine imaging, a bolus of gadodiamide was administered. Short-axis images of entire left ventricle (LV) were acquired with a breath-hold T1-weighted segmented inversion-recovery turbo fast low-angle shot (FLASH) sequence. Agreement for myocardial hyperenhancement (HE) mass between field strengths was assessed with Bland-Altman method; agreement for detection and transmural extent of HE was assessed with kappa statistics. Intra- and interobserver reproducibility of mass and transmural extent of HE were assessed at 1.5 and 3.0 T. RESULTS: Bland-Altman analysis revealed no systematic bias (mean difference, 0.2 g; 95% confidence interval: -0.7 g, 1.2 g) and acceptable limits of agreement (-3.3 to 3.8 g) between field strengths for HE mass. HE mass measurements were strongly correlated (R(2) = 0.99); there was no significant difference in measurements at 1.5 and 3.0 T (28.1 g +/- 15.7 [22.6% +/- 10.9 of LV mass] vs 27.8 g +/- 15.7 [22.3% +/- 10.7 of LV mass], respectively; P = .599). For all segments, there was a high degree of agreement for HE detection (kappa = 0.90) and transmural grade (kappa = 0.79) between field strengths. Intra- and interobserver variability were low between both field strengths. Initial inversion time selected to null the signal of normal myocardium at 3.0 T was 57 msec +/- 20 longer than at 1.5 T (P < .01). CONCLUSION: By using the same turbo FLASH MR pulse sequence, there was strong agreement in mass and transmural extent of myocardial HE between 1.5 and 3.0 T.

Aged↗

PubMed2006

Effects of steady state free precession parameters on cardiac mass, function, and volumes.

PURPOSE: We aimed to investigate comparability of LV volumes, function, and mass acquired with three steady-state free precession (SSFP) pulse sequences, simulating typical vendor and protocol specific differences in data acquisition. METHODS: Twenty-one healthy subjects (11 male and 10 female; age range 23-49) underwent cardiac magnetic resonance (CMR) imaging at 1.5 Tesla (T). A complete stack of short-axis views covering the entire left ventricle (LV) were acquired for each of the three SSFP sequences, differing in the interslice gap and slice thickness (7 mm with no gap (7/0 mm); 7 mm with a 3 mm gap (7/3 mm) and 6 mm with a 4 mm gap (6/4 mm)) with slight variations in acquisition parameters. For each sequence, the LV volumes, function, and mass were determined. Intra- and inter-observer variability and inter-study reproducibility were assessed for all protocols. RESULTS: All LV volumes, function and mass parameters were similar for the three SSFP sequences (P > 0.05 for all). The LV ejection fraction for the 7/3 mm sequence was 67.2 +/- 6.0, 67.4 +/- 5.3 for the 7/0 mm sequence, and the 6/4 mm sequence was 69.2 +/- 5.7. The LV mass ranged from 119.8 +/- 32.4 for the 7/3 mm sequence to 122.2 +/- 34.0 for the 7/0 mm sequence. Variabilities were low with no difference in variability between the sequences. CONCLUSION: The three SSFP pulse sequence techniques resulted in similar LV volume, function, and mass measurements with no difference in observer and interstudy variabilities. This may allow application and transfer of LV volume studies and databases based on different imaging parameters, at different CMR sites, with a given post-processing method. Future multi-centre studies may now be in a position to consider multi-vendor study designs for LV volume studies.

Adult↗

PubMed2006

Connectivity-based parcellation of human cortex using diffusion MRI: Establishing reproducibility, validity and observer independence in BA 44/45 and SMA/pre-SMA.

The identification of specialized, functional regions of the human cortex is a vital precondition for neuroscience and clinical neurosurgery. Functional imaging modalities are used for their delineation in living subjects, but these methods rely on subject cooperation, and many regions of the human brain cannot be activated specifically. Diffusion tractography is a novel tool to identify such areas in the human brain, utilizing underlying white matter pathways to separate regions of differing specialization. We explore the reproducibility, generalizability and validity of diffusion tractography-based localization in four functional areas across subjects, timepoints and scanners, and validate findings against fMRI and post-mortem cytoarchitectonic data. With reproducibility across modalities, clustering methods, scanners, timepoints, and subjects in the order of 80-90%, we conclude that diffusion tractography represents a useful and objective tool for parcellation of the human cortex into functional regions, enabling studies into individual functional anatomy even when there are no specific activation paradigms available.

Adult↗

PubMed2006

Functional and structural vascular remodeling in elite rowers assessed by cardiovascular magnetic resonance.

OBJECTIVES: We aimed to noninvasively quantify the effects of chronic exercise training on both peripheral and central conduit artery function and structure with high-resolution magnetic resonance imaging (MRI). BACKGROUND: Physical activity has well-known beneficial effects on vascular function in subjects with endothelial dysfunction. Exercise also leads to beneficial effects on endothelial function in elderly athletes, possibly contributing toward the reduced risk from coronary artery disease in this age group. However, conflicting data exist on the training effects in the younger population. METHODS: A total of 49 young (age 20 to 35 years) nonsmoking subjects, comprising elite rowers and age- and gender-matched sedentary control subjects, underwent MRI (1.5-T). The ascending, the proximal descending, and the distal descending aorta, and the common carotid artery and the brachial artery were assessed for diastolic and systolic area and distensibility. Endothelial-dependent and -independent brachial artery dilatation were also assessed by cine MRI. RESULTS: Rowers showed vascular remodeling with enlarged brachial (by 51%, p < 0.001) and reduced central conduit artery cross-sectional areas (by up to 28% [e.g., distal descending aorta], p < 0.001). Vessel distensibilities (mm Hg(-1)) were similar for elite rowers when compared with sedentary control subjects at all levels of the aorta and the carotid and brachial artery (p > 0.05 for all). Endothelial-dependent dilation (percentage and mm2) was similar for rowers and control subjects (p > 0.05). However, rowers showed reduced absolute (by 33%) endothelial-independent dilation (p < 0.001). CONCLUSIONS: Young elite rowers demonstrate normal endothelial-dependent but reduced endothelial-independent dilation. Chronic, whole body, combined endurance- and strength-training does not lead to changes in arterial stiffness but to vascular remodeling.

Adult↗

PubMed2006

MRI and clinical studies of facial and bulbar muscle involvement in MuSK antibody-associated myasthenia gravis.

A proportion of patients with myasthenia gravis (MG) without acetylcholine receptor (AChR) antibodies have antibodies to muscle-specific kinase (MuSK). MG with MuSK antibodies (MuSK-MG) is often associated with persistent bulbar involvement, including marked facial weakness and tongue muscle wasting. The extent of muscle wasting in MuSK-MG, and whether it is also found in the few acetylcholine receptor (AChR-MG) patients who have persistent bulbar involvement, is not clear. We studied 12 MuSK-MG patients and recruited 14 AChR-MG patients matched broadly for age, sex ratio, duration of disease and degree of ocular, bulbar and facial weakness. We used coronal and sagittal T1-weighted (T1W) and T2-weighted (T2W) magnetic resonance imaging (MRI) to assess muscle wasting in facial and tongue muscles. Hyperintense signal on T1W MRI and comparison of axial T1W sequences with cUTE sequences were used to assess fibrous/fatty tissue in the tongue. We compared the results with those of four patients with myotonic dystrophy and 12 healthy individuals. We correlated the changes with clinical and treatment histories, and established a new ocular-bulbar-facial-respiratory (OBFR) score. At the time of study, none of the clinical measures, including the OBFR score, differed between the two MG groups. MRI demonstrated thinning of the buccinator, orbicularis oris (O.oris) and orbicularis oculi (O.oculi) muscles in MuSK-MG patients compared with healthy controls, whereas thinning of these muscles was not significant in AChR-MG. Tongue areas with T1W high signal were increased in MuSK-MG patients and the intensity of the signal on axial T1W sequences was greater in MuSK-MG than in controls. To look for possible correlations between imaging and clinical findings, we pooled results from all MG patients. The duration of treatment with prednisolone at >40 mg on alternate days (AD) correlated positively with the percentage of tongue area with high signal (P = 0.006) and negatively with MRI measurements of individual muscles and with the mean muscle dimensions (P = 0.001). The new OBFR score correlated positively with current Myasthenia Gravis Foundation of America grades and with the percentage of high signal (P = 0.004) and negatively with the mean muscle dimensions (P < 0.001). The results show that bulbar and facial muscle weakness and wasting are associated with significant muscle atrophy and fatty replacement in MuSK-MG, which was not found in the AChR-MG patients. MuSK antibodies per se may predispose to muscle thinning, but the difficulties in obtaining clinical remission under steroid therapy in some patients, resulting in long duration of treatment with higher doses (>40 mg AD), may be an additional factor.

Adolescent↗

PubMed2006

Myocardial tissue phase mapping with cine phase-contrast mr imaging: regional wall motion analysis in healthy volunteers.

PURPOSE: To establish prospectively a database of normal three-dimensional systolic and diastolic endocardial and epicardial velocity values for all myocardial segments in healthy volunteers by using cine phase-contrast velocity magnetic resonance imaging, also called tissue phase mapping (TPM). MATERIALS AND METHODS: The study was approved by the institutional ethics committee and was conducted according to principles of the Declaration of Helsinki; each subject provided informed written consent. Ninety-six healthy volunteers (57 [59%] men, 39 [41%] women; mean age, 38 years +/- 12 [standard deviation]) underwent cardiac phase-contrast imaging with a black blood segmented k-space gradient-echo sequence for the analysis of three-dimensional myocardial velocity with high spatial resolution at 1.5 T on basal, midventricular, and apical short-axis views. Eighteen consecutive volunteers were imaged twice to determine interstudy reproducibility, and intra- and interobserver variability values were analyzed. Systolic and diastolic velocity curves were analyzed for peak velocity and time to peak velocity in the radial, circumferential, and longitudinal directions, as well as for torsion rate and longitudinal strain rate. Mixed-effects models with a random intercept for volunteers were used to test differences among the three ventricular sections and the transmural, endocardial, and epicardial parameters. RESULTS: TPM enabled reproducible assessment of myocardial velocity with small intra- and interobserver variability values. Systolic peak radial velocity was lowest at the apical level (P < .001); diastolic peak radial velocity was similar at all three myocardial levels (P = .73). As viewed from the apex, a relative counterclockwise rotation during systole was followed by a relative clockwise rotation of the apex against the base. Diastolic and systolic peak longitudinal velocity values decreased from base to apex (P < .001). A gradient between endocardium and epicardium was observed for radial velocity values, with greater endocardial velocity values (P < .001). CONCLUSION: TPM is a reproducible comprehensive modality for assessment of regional wall motion, and intra- and interobserver variability values are low.

Adult↗

PubMed2006

Sex-specific characteristics of cardiac function, geometry, and mass in young adult elite athletes.

PURPOSE: To study young adult elite athletes with age- and sex-matched sedentary controls to assess sex-specific differences for left ventricular (LV) and right ventricular (RV) volumes and mass as well as for LV contraction and relaxation. MATERIALS AND METHODS: A total of 23 male athletes (mean age 25 +/- 4 years, training 22 +/- 7 hours/week in rowing, swimming, or triathlon) and 20 female athletes (mean age 24 +/- 4 years, training 19 +/- 5 hours/week in rowing, swimming, or triathlon) and age- and sex-matched sedentary controls (21 male/17 female) underwent cardiovascular magnetic resonance (CMR) imaging (1.5 Tesla). Cardiac phase contrast imaging using a black-blood k-space segmented gradient echo sequence was used for analysis of cardiac contraction and relaxation and steady-state free-precession cine images were acquired for determination of cardiac volumes and mass. RESULTS: Male and female athletes showed similar increases in LV and RV volume and mass indices when compared to controls (ranging between 15% and 42%). No sex-specific differences in training effect on LV and RV volumes, mass indices, and ejection fractions, as well as LV to RV ratios of these volume and mass indices (parameters of balanced LV and RV dilatation and hypertrophy) were observed (all P for interaction >0.05). Similarly, no sex-specific differences in training effect on cardiac contraction and relaxation were found (all P for interaction >0.05). CONCLUSION: Young adult elite athletes do not show sex-specific adaptive structural and functional changes to exercise training in accordance with the benign nature of the hypertrophy associated with athlete's heart.

Adult↗

PubMed2006

Determination of cardiac volumes and mass with FLASH and SSFP cine sequences at 1.5 vs. 3 Tesla: a validation study.

PURPOSE: To compare cardiac cine MR imaging using steady state free precession (SSFP) and fast low angle shot (FLASH) techniques at 1.5 and 3 T, and to establish their variabilities and reproducibilities for cardiac volume and mass determination in volunteers. To assess the feasibility of SSFP imaging in patients at 3 T and to determine comparability to volume data acquired at 1.5 T. MATERIALS AND METHODS: Ten healthy volunteers underwent cardiac magnetic resonance imaging using SSFP and segmented gradient-echo FLASH, using both a 1.5 and a 3 T MR system on the same day. Ten patients with impaired left ventricular (LV) function were also studied at both field strengths with SSFP. RESULTS: For both SSFP and FLASH, field strength had no effect on the quantification of LV and right ventricular (RV) volumes, mass, or function (P > or = 0.05 for field strength for all parameters). At both 1.5 and 3 T, SSFP yielded smaller LV mass (e.g., at 3 T 109 +/- 30 g vs. 142 +/- 37 g; P = 0.011) and larger LV volume (e.g., at 3 T end-diastolic volume 149 +/- 37 mL vs. 133 +/- 31 mL at 5 T; P = 0.041) measurements than FLASH. In patients with reduced LV function, all volume and mass measurements were again similar for SSFP sequences at 1.5 vs. 3 T. In volunteers and patients, measurement variabilities for LV parameters were small for both field strength and sequences, ranging between 3.7% and 10.7% for mass. CONCLUSION: Compared to 1.5 T, cardiac cine MR imaging at 3 T, using either FLASH or SSFP sequences, is feasible and highly reproducible. Field strength does not have an influence on quantification of cardiac volume or mass, but the systematic overestimation of LV mass and underestimation of LV volume by FLASH compared to SSFP is present at both 1.5 and 3 T. Normal values for cardiac volumes and mass established at 1.5 T can be applied to scans obtained at 3 T.

Adult↗

PubMed2006

Clinical ultrashort echo time imaging of bone and other connective tissues.

The background underpinning the clinical use of ultrashort echo time, SPRITE and other pulse sequences for imaging bone and other connective tissues with short T2 is reviewed. Features of the basic physics relevant to UTE imaging are described, including the consequences when the radiofrequency pulse duration is of the order of T2 so that rotation of tissue magnetization into the transverse plane is incomplete. Consequences of the broad linewidth of short T2 components are also discussed, including partial saturation by off-resonance fat suppression pulses as well as those used in multislice and multiecho imaging. The need for rapid data acquisition of the order of T2 is explained. The basic two-dimensional UTE pulse sequence with its half excitation pulse and radial imaging from the centre of k-space is described, together with options that suppress fat and/or reduce the signal from long T2 components. The basic features of SPRITE and other sequences with very short TE are described. Image interpretation is discussed. Clinical features of the imaging of cortical bone, tendons, ligaments, menisci, periosteum and the spine are illustrated. The source of the short T2 signal in these tissues is predominantly collagen and water tightly bound to collagen. Short T2 components in all of these tissues are detectible and may show high signals. Possible future developments are outlined, as are technical limitations of clinical magnetic resonance systems.

Animals↗

PubMed2006

Cardiac cine MR-imaging at 3T: FLASH vs SSFP.

The implications of an increase in field strength, from 1.5 T to 3 T, for routine functional cardiac examinations have been systematically investigated. Flip angle optimization was carried out for identical SSFP and FLASH cine imaging sequences at 1.5 T and 3 T, which supported the use of 20 degrees (FLASH 1.5 T and 3 T) and >60 degrees (SSFP 1.5 T and 3 T). The optimized sequences were applied in a study of cardiac function in a group of ten normal volunteers. Both SSFP and FLASH sequences showed significant SNR increases in the myocardium and blood at 3 T compared with 1.5 T, increases of 48% and 30% (myocardium and blood, respectively) for the SSFP sequence and 19% and 13% for the FLASH sequence. The SSFP sequence also showed a significant increase in CNR (22%). Image quality assessment revealed that the SSFP acquisitions were superior to FLASH at both field strengths. Although SSFP contained more artifacts at 3 T, they would not prevent its clinical use. We conclude that cardiac functional examinations at 3 T should use SSFP sequences.

Artifacts↗

PubMed2005

Reconstruction as a source of artifact in non-gated single-shot diffusion-weighted EPI.

A controversy has existed over the requirement to cardiac gate diffusion-weighted MRI acquisitions of the brain. Conventional wisdom suggests gating to be a necessary requirement to allow acquisition of accurate data, but recent applications find gating not necessary. The signal-to-noise and acquisition duration of these two approaches can be quite different; thus, this difference in methodology is important. This is particularly relevant when performing quantitative work such as diffusion tensor imaging. Here, the convention to gate is explained as being due to the historical use of low spatial resolution and more recently to the use of different reconstruction approaches. It is demonstrated that the Margosian reconstruction approach only yields high quality results when used in a gated fashion. Zero padding of the acquisition matrix provides an alternative reconstruction method that is not found to accentuate the artifacts that are due to pulsatile motion in the diffusion-weighted acquisition and thus do not require a gated acquisition. The relative merits of each reconstruction approach are discussed, including estimates of the relative signal-to-noise ratio and resolution benefits. It is concluded that both gated methods and non-gated methods can each provide high quality results with appropriate reconstruction methods.

Artifacts↗

PubMed2005

Hypertrophic cardiomyopathy in Noonan Syndrome closely mimics familial hypertrophic cardiomyopathy due to sarcomeric mutations.

A 27 year old female with Noonan syndrome and hypertrophic cardiomyopathy underwent cardiovascular magnetic resonance imaging. These images showed asymmetrical septal hypertrophy with maximal left ventricular end-diastolic wall thickness of 25 mm. Following administration of gadolinium, areas of hyperenhancement were seen in the anterior, anteroseptal and lateral walls. This is the first report of focal gadolinium hyperenhancement in hypertrophic cardiomyopathy due to Noonan syndrome and suggests that myocardial fibrosis can be imaged by MR hyperenhancement as seen previously in sarcomeric hypertrophic cardiomyopathy.

Adult↗

PubMed2005

Quantitative investigation of connections of the prefrontal cortex in the human and macaque using probabilistic diffusion tractography.

The functions of prefrontal cortex (PFC) areas are constrained by their anatomical connections. There is little quantitative information about human PFC connections, and, instead, our knowledge of primate PFC connections is derived from tracing studies in macaques. The connections of subcortical areas, in which white matter penetration and hence diffusion anisotropy are greatest, can be studied with diffusion-weighted imaging (DWI) tractography. We therefore used DWI tractography in four macaque and 10 human hemispheres to compare the connections of PFC regions with nine subcortical regions, including several fascicles and several subcortical nuclei. A distinct connection pattern was identified for each PFC and each subcortical region. Because some of the fascicles contained connections with posterior cortical areas, it was also possible to draw inferences about PFC connection patterns with posterior cortical areas. Notably, it was possible to identify similar circuits centered on comparable PFC regions in both species; PFC regions probably engage in similar patterns of regionally specific functional interaction with other brain areas in both species. In the case of one area traditionally assigned to the human PFC, the pars opercularis, the distribution of connections was not reminiscent of any macaque PFC region but, instead, resembled the pattern for macaque ventral premotor area. Some limitations to the DWI approach were apparent; the high diffusion anisotropy in the corpus callosum made it difficult to compare connection probability values in the adjacent cingulate region.

Adult↗

PubMed2005

The evolution of prefrontal inputs to the cortico-pontine system: diffusion imaging evidence from Macaque monkeys and humans.

The cortico-ponto-cerebellar system is one of the largest projection systems in the primate brain, but in the human brain the nature of the information processing in this system remains elusive. Determining the areas of the cerebral cortex which contribute projections to this system will allow us to better understand information processing within it. Information from the cerebral cortex is conveyed to the cerebellum by topographically arranged fibres in the cerebral peduncle - an important fibre system in which all cortical outputs spatially converge on their way to the cerebellum via the pontine nuclei. Little is known of their anatomical organization in the human brain. New in vivo diffusion imaging and probabilistic tractography methods now offer a way in which input tracts in the cerebral peduncle can be characterized in detail. Here we use these methods to contrast their organization in humans and macaque monkeys. We confirm the dominant contribution of the cortical motor areas to the macaque monkey cerebral peduncle. However, we also present novel anatomical evidence for a relatively large prefrontal contribution to the human cortico-ponto-cerebellar system in the cerebral peduncle. These findings suggest the selective evolution of prefrontal inputs to the human cortico-ponto-cerebellar system.

Adult↗

PubMed2005

Left ventricular non-compaction: insights from cardiovascular magnetic resonance imaging.

OBJECTIVES: We aimed to test the diagnostic accuracy of cardiovascular magnetic resonance (CMR) imaging in distinguishing pathological left ventricular non-compaction (LVNC) from lesser degrees of trabecular layering seen in healthy volunteers and, in those with cardiomyopathies and concentric left ventricular hypertrophy, potential differential diagnoses. We hypothesized that pathological trabeculation could be distinguished by determining the ratio of non-compacted to compacted myocardium (NC/C ratio). BACKGROUND: Left ventricular non-compaction is characterized by a non-compacted myocardial layer in the left ventricle. Cardiovascular magnetic resonance images this layer with unprecedented quality, particularly in the ventricular apex, where echocardiography has inherent difficulties. METHODS: We analyzed magnetic resonance cine images, using the 17-segment model in 45 healthy volunteers, 25 athletes, 39 patients with hypertrophic cardiomyopathy and 14 with dilated cardiomyopathy, 17 with hypertensive heart disease, and 30 with aortic stenosis, as well as images from 7 patients previously diagnosed with LVNC whose diagnoses were supported by additional features. RESULTS: Areas of non-compaction were common and occurred more frequently in all groups studied in apical and lateral, rather than in basal or septal, segments. A NC/C ratio of >2.3 in diastole distinguished pathological non-compaction, with values for sensitivity, specificity, and positive and negative predictions of 86%, 99%, 75%, and 99%, respectively. CONCLUSIONS: Left ventricular non-compaction is diagnosed accurately with CMR using the NC/C ratio in diastole.

Adolescent↗

PubMed2005

Ultrashort TE chemical shift imaging (UTE-CSI).

A fundamental modification to the conventional chemical shift imaging (CSI) method is described that improves the imaging of species with short T2's (i.e., less than approximately 2 ms). This approach minimizes the delay before each k-space point is collected. This results in different time delays, T(d), for different free induction decay (FID) acquisitions in k-space. On a clinical 1.5 T system this yields an effective delay due to transmit/receive switching of 70 micros and an echo time (TE) from the center of the excitation pulse to the center of k-space of 170 micros, as compared with 1-2 ms for conventional CSI techniques. Using this method, the signal decay before acquisition is greatly reduced, thus enabling imaging of species with very short T2)(e.g., 200 micros) and increasing the signal-to-noise ratio (SNR) of species with intermediate T2. Increases in the SNR of the short T2 components of 23Na in the heart, and 31P acquisitions of bone are about 27% and 400%, respectively, compared to an optimized conventional CSI approach. The imperfections of this approach are also described, and the magnitude of the resultant image artifacts is quantified for different practical imaging situations. These artifacts were not found to be significant in the described applications. This new method allows us to obtain information on short T2 components without degrading the image quality from long T2 components.

Algorithms↗

PubMed2005

Partial fourier partially parallel imaging.

The techniques of partial Fourier (PF) and partially parallel imaging have been combined using a constrained reconstruction technique. The benefits compared with the individual techniques are reduced imaging time and/or an increase in signal-to-noise ratio. Low-resolution phase maps and coil sensitivities may be obtained using autocalibration or from a prescan followed by additional processing. Minor phase artifacts that are introduced by relying on conjugate symmetry can be reduced using a novel regularization scheme to vary the degree to which PF is used in the reconstruction. A nonrectilinear reconstruction algorithm is presented and the potential for motion artifact reduction is investigated using robust reconstruction.

Algorithms↗

PubMed2005

Magnetic resonance imaging of cortical bone with ultrashort TE pulse sequences.

PURPOSE: Normal adult cortical bone has a very short T(2) and characteristically produces no signal with pulse sequence echo times (TEs) routinely used in clinical practice. We wished to determine whether it was possible to use ultrashort TE (UTE) pulse sequences to detect signal from cortical bone in human subjects and use this signal to characterise this tissue. SUBJECTS AND METHODS: Seven volunteers and 10 patients were examined using ultrashort TE pulse sequences (TE=0.07 or 0.08 ms). Short and long inversion as well as fat suppression pulses were used as preparation pulses. Later echo images were also obtained as well as difference images produced by subtracting a later echo image from a first echo image. Saturation pulses were used for T(1) measurement and sequences with progressively increasing TEs for T(2)* measurement. Intravenous gadodiamide was administered to four subjects. RESULTS: Signal in cortical bone was detected with UTE sequences in children, normal adults and patients. This signal was usually made more obvious by subtracting a later echo image from the first provided that the signal-to-noise ratio was sufficiently high. Normal mean adult T(1)s ranged from 140 to 260 ms, and mean T(2)*s ranged from 0.42 to 0.50 ms. T(1) increased significantly with age (P<.01). Increased signal was observed after contrast enhancement in the normal volunteer and the three patients to whom it was administered. Reduction in signal from short T(2) components was seen in acute fractures, and increase in signal in these components was seen with new bone formation after fracture malunion. In a case of osteoporosis, bone cross-sectional area and signal level appeared reduced. CONCLUSION: Signal can be detected from normal and abnormal cortical bone with UTE pulse sequences, and this can be used to measure its T(1) and T(2)* as well as observe contrast enhancement. Difference images are of value in increasing the conspicuity of cortical bone and observing abnormalities in disease.

Adolescent↗